DESCRIPTION (provided by the applicant: Intestinal microsporidiosis is a major complication in 15 percent of AIDS patients. These protozoal parasites also cause "traveler's" diarrhea in healthy individuals and opportunistic infections in transplant recipients. The signals involved in activating the environmentally resistant microsporidial spore to initiate infection within a susceptible host are currently unknown. Preliminary data obtained by the Principal Investigator suggest that reactive oxygen species likely contribute to parasite activation and initiation of infection. The Principal Investigator proposes to test the hypothesis that host cells generate the necessary signals for parasite activation by evaluating parasite infectivity in cell culture and animal model systems. The rationale for the proposed research is that identifying the signals involved in activation of these parasites will lead to more effective means of controlling or eliminating microsporidiosis in humans. Results obtained from the proposed research will be useful in developing novel strategies that will reduce or eliminate infection, thereby improving the quality of life of patients with microsporidiosis. The purpose of this proposed Mentored Clinical Scientist Development (K08) Award is to provide the Principal Investigator with the mentoring and resources in order to become a completely independent academic clinician-scientist. The Principal Investigator has completed didactic and clinical training, has demonstrated scientific productivity, but requires more supervised research experience prior to starting an independent research career. Career development for the Principal Investigator under this award will consist of initiating and completing the proposed research experiments; preparing data for submission to professionally refereed journals; supporting continued attendance and presentations at scientific conferences; and applying for future research grant support based on results obtained from the proposed research. With her professional training in veterinary medicine and graduate training in comparative pathology, the Principal Investigator will be positioned to pursue an independent and productive career in the field of comparative medical research.